Automatic power control system



Jan. 13, 1959 J. G. DWYER AUTOMATIC POWER CONTROL SYSTEM Filed July 2. 1953 ENGINE 5 UNIT IN V EN TOR.

JOHN G. DWI ER hired States d ce 2,869,039 AUTOMATIC POWER CONTRCL EBYSTEM John G. Dwyer, Westfield, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. 3., a corporation of Delaware Application July 2, 1953, Serial No. 365,659 1 Claim. (Cl. 317-13) This invention relates to automatic electric power cutoff systems, and is particularly directed to a novel system of the type that is actuated by changes in electrical conditions in the feed line of a motor such as those produced by increased resistance to the motor drive.

The invention has been found to be especially advantageous in remote control systems for motors, and has been developed for marine engines connected to the propeller shaft through a clutch engaged and disengaged by a servomotor controlled from the bridge or other remote point, though obviously it is applicable to other types of installations. In such remote control systems the servomotor is required to close the clutch to the point where the clutch engaging pressure is adequate for proper operation, without applying excessive stress after the clutch is engaged. This result has heretofore been attained by the use of a cut-out switch system mechanically operated to open the servomotor circuit when the clutch has been driven to a predetermined position. However, the correct position of the clutch for proper engagement is quite critical, and moreover it changes with wear and with variations in operating conditions; so that frequent adjustment or" the switch opening means is required with such systems.

The general object of this invention is to provide a power cut-off system that does not require such adjust,- ment, but will function when a predetermined motor drive pressure is reached, so that a clutch driven into engaging position by the motor will be automatically seated with the same pressure regardless of wear and changes in other conditions. A further object is to pro- Vide such a system with elfective electrical means for ready and precise adjustment of the cut-oh conditions.

The invention is moreover applicable to the solution of other problems in which automatic operation of a cut-out or other device in response to changes in line conditions is required. In particular, when the line current increases, the increase frequently is too sli ht and slow to produce the desired rapid action by simple practical means, especially when the line is directly connected to the main power source. A feature of the invention is the utilization of the voltage drop, which occurs when the current rises, to actuate the cut-out switch or other change-responsive device. This arrangement is especially advantageous when relays are used in-such device. 7

Another more specific feature is the actuation of a control relay by rectified direct current derived from the A. C. power line of the apparatus to be controlled, such as a motor, arranged to release the relay when the power line voltage drops to a determined extent, a condition characteristic of overloading or stalling of the motor. This is particularly desirable where rapid, accurate and uniform relay release is important, for if a relay is employed under these conditions to open when line conditions change, it would normally be of the A. C. type; whereas, D. C. relays have much more reliable uniform release voltage conditions than A. C. relays,

2 A further feature is the provision of means for adjusting the D. C. voltage applied to a control relay so that it will release when a determined voltage drop occurs in A. C. power line from which the D. C. voltage is obtained.

The actuating'voltage of relays is generally substantially higher than the releasing voltage; and a feature of cation is an arrangement for initially applying to a circuit control relay a higher voltage sufficient to close its contacts, and thereafter applying to the relay a substantially lower voltage derived from the power line to be controlled, the relay being opened promptly by cutting off the lower voltage.

While motor-operated clutches frequently are operated 'by worm gears or other mechanisms which hold the clutch in place after the motor stops, a widely used type of clutch has a detent arrangement for holding the clutch in position after clutch-shifting power is released; and, a specific purpose of this invention is to provide an automatic clutch-shifting motor control that is adapted to move the clutch positively and uniformly to a point where release of the motor drive will result in proper detent engagement.

tier purposes are to devise a system that is suitable for use in established remote drive control installations, especially under marine operating conditions, one that is simple and reliable and which utilizes standard electrical units.

These and other objects and advantages of the invention will appear more fully hereinafter from the detailed description and the accompanying drawing, which is a simplified diagram illustrating an embodiment of the invention applied to a marine installation. It is to be expressly understood, however, that the drawing is for the purposes of illustration and description, and is not to be construed as defining the limits of the invention.

The specific embodiment shown in the drawing is incorporated in a system for controlling the operation of a drive system connected to engine 1, which drives a load 2 such as a propeller shaft through a clutch 3 arranged for movement into and out of engaged position by means of servomotor 4 through clutch drive 5, which may be any of the large number or" drive arrangements employed for clutch operation.

The servomotor 4 is energized from A. C. power source 6 which, as shown, is of the two-phase type. Means are provided for reversing the servomotor 4 and thereby either closing or opening the clutch 3 as desired. Various arrangements for this purpose are known, including synchro systems which accomplish the reversal electrically from a remote control point; but for simplicity, a standard type reversing switch 7 is disclosed, mechanically operated by lever 8, which may be located at any desired remote point such as the bridge of a vessel. A transformer 9 is advantageously provided in power line it between source 6 and servomotor 4 in order to provide proper voltage for said motor and for other purposes hereinafter set forth.

An arrangement is provided for automatically closing line It and energizing servomotor 4 when control lever 8 is shifted, and for opening said line to stop the servornotor when clutch 3 has been shifted into the desired position. This arrangement includes a relay system which is operated from a D. C. power source 11 and comprises an operating relay 12 connected at one side to the negative lead 13 from source 11 and at the other side to positive lead 14 from said source through an arrangement which momentarily closes the connection when lever 8 is shifted. In the simplified arrangement shown, a normally open switch 15 is engaged by a spring detent arm 16 which normally rests in notches 17 in detent sector 18 mounted on lever 8, arm 16 being shifted by the elevated cam section 19 of said sector between notches 17 so as to close switch 15 while lever 8 is being shifted. A power relay Ed is connected at one side through the normally open contacts of operating relay '12 to positive lead and at the other side to negative lead The normally open contacts of relay 20 are connected in the power leads 10 extending from source 6 to transformer 9.

A D. C. holding circuit for operating relay 12, energized from power line 10, is provided. it comprises transformer 21, whose primary is connected to line 10 at the motor side of transformer 9 and whose secondary is connected to rectifying means such as rectifier bridge The negative output terminal of the bridge is connected to D. C. negative lead 13 while the positive bridge terminal is connected through rheostat 23 to the positive terminal of operating relay 12.

The arrangement is shown with the clutch 3 in open position. in operation, in order to actuate servornotor 4 to close the clutch, lever d is shifted to the left, operating reversing switch 7 to make the proper connections for forward drive of the servomotor 4. During the movement of lever 53, switch 15 will be closed for a brief period as detent arm 16 passes from one switch notch 17 to the other, energizing operating relay i2 and closing its terminals, which will energize line relay 20 and connect the servomotor 4 to the power source 6, starting the motor. Transformer 21 will simultaneously be energized, which will apply a D. C. voltage from bridge 22 through rheostat 23 across relay 12, holding the latter relay and relay 20 in closed position after lever S has reached its terminal position and the movement of detent 1.6 into notch 17 has opened switch 15.

Motor 4 will thus continue to operate until clutch 3 is seated and offers increasing resistance to motor 4, thereby decreasing the impedance of the motor and the voltage in power line 10, correspondingly reducing the voltage through transformer 21 and the D. C. voltage applied to relay 12, so that the latter relay Will open, releasing power relay 20 and disconnecting power line 10 from servomotor The provision of rheostat 23 in the holding circuit for operating relay 12 makes it possible to regulate with great accuracy the holding voltage applied to the latter relay, which of course has a great deal lower value than the required relay closing voltage which is applied from source 11. This adjustment makes it possible not only to set the system for the release of relay 12 and the disconnecting of vservomotor t when any predetermined voltage drop occurs in line 10, but also to adjust the system with great accuracy to the particular release voltage requirements of an individual relay 12, since different relays have substantial variations in release voltage in actual practice.

The inclusion of a transformer 9 not only permits the proper voltage to be applied to servomotor 4, but also provides a circuit in which increased resistance through operation of said motor will result in a much greater voltage drop in the motor feed line 10 than would occur if the motor were directly connected to main power source; and the increased voltage drop improves substantially the accuracy and sensitivity of the relay releasing system described.

As already indicated, in certain types of clutch drive units 5, a detent device operates to hold clutch 3 in place at the desired points. A simplified illustrative embodiment of this feature is shown, including a clutch shifting yoke 24 carrying a spring pressed detent 2.5 engaging notches in fixed detent bar 27. Certain arrangements of this type are designed so that in closing clutch 3 the latter is shifted slightly beyond the detent point and drops into detent position when the power is released. The disclosed system is designed so that it may function in this manner, since the complete release of the power supply to servornotor t permits the clutch 3 to adjust itself to the proper detent position.

While remote clutch control systems of the indicated type are frequently designed to operate two clutches, one for forward drive and one for reverse drive, the application of the invention to such systems is obvious; and consequently the invention is illustrated in its application to the simpler system for closing and opening a single clutch. Also, while two relays are provided, one of which controls the other, an arrangement that enhances the efilciency of the arrangement, the invention is not limited to such an arrangement, since other relay systems with fewer or more relays may be used.

Moreover, while the invention is especially and unexpectedly advantageous when applied to installations of the types indicated, it may be used in its broader phases for other types of installation and control where a voltage drop in a supply line to a motor or other apparatus is utilized to accomplish a given result, and particularly to open a relay system, which may disconnect the power line.

Although only one embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design, arrangement and interconnection of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

An electric power control system comprising a motor, an alternating current source for energizing said motor, a first switch connected between said alternating current source and said motor, a first relay for operating said first switch, a direct current source, a second switch connecting said first relay to said direct current source, a second M relay for operating said second switch, means connected be ween said direct current line and said second relay for momentarily energizing said second relay to energize said first relay and operate said first switch, a holding circuit for energizing said first and second relays including a rectifier connected between said alternating current source and said second relay, said rectifier being responsive to voltage variations of said alternating current source so that a reduction in alternating current source voltage deenerg izes said first and second relays and said first switch opens to deenergize said motor.

References (Cited in the file of this patent UNTTED STATES PATENTS 1,332,631 Morse Mar. 2, 1920 1,380,823 Matthews June 7, 1921 1,980,142 OHagan Nov. 6, 1934 2,203,920 OHagan June 11, 1940 2,376,658 Charbonneau et al. May 22, 1945 2,426,071 Veinott Aug. 19, 1947 

